Question

我有两个固定顶部导航栏，第一个导航栏的下拉菜单与第二个导航栏重叠。尝试弄乱z索引，定位和溢出。。还发现了一些有点相关的问题，但似乎无济于事。任何想法可能是什么原因造成的？

链接到 FIDDLE

下图显示了问题的性质（第二导航栏重叠下拉菜单）：

示例：

<!DOCTYPE html>
<html>
<head>
<meta>
<title>Navbar overlapping dropdown-menu</title>

<!-- Bootstrap 4 cdn's & jquery dependency -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

</head>
<body>

    <!-- first navbar with dropdown-menu -->
    <nav class="navbar bg-dark fixed-top navbar-expand-sm">
      <div class="collapse navbar-collapse">
        <ul class="navbar-nav">
          <li class="nav-item dropdown">
            <a class="nav-link dropdown-toggle" href="#" role="button" data-toggle="dropdown"> Dropdown </a>
            <div class="dropdown-menu">
              <a class="dropdown-item" href="#"> 1 </a>
                  <a class="dropdown-item" href="#"> 2 </a>
              <a class="dropdown-item" href="#"> 3 </a>
              <a class="dropdown-item" href="#"> 4 </a>
            </div>
          </li>
        </ul>
      </div>
    </nav>


    <!-- second navbar with top offset -->
    <nav class="navbar bg-primary fixed-top navbar-expand-sm" style="top:56px!important;">
    <p>hello world</p>
    </nav>

</body>
</html>

Answer 1

您是正确的，这是z-index问题。尝试添加一些样式以使z-index的第二个navbar降低。弄乱z-index时，请记住要调整引起问题的兄弟姐妹。调整.dropdown-menu不会执行任何操作，因为问题出在父元素上。

您可以这样做：

.navbar {
  z-index: 90;
}

.navbar+.navbar {
  z-index: 80;
  top:56px;
}

<!DOCTYPE html>
<html>

<head>
  <meta>
  <title>Navbar overlapping dropdown-menu</title>

  <!-- Bootstrap 4 cdn's & jquery dependency -->
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

</head>

<body>

  <!-- first navbar with dropdown-menu -->
  <nav class="navbar bg-dark fixed-top navbar-expand-sm">
    <div class="collapse navbar-collapse">
      <ul class="navbar-nav">
        <li class="nav-item dropdown">
          <a class="nav-link dropdown-toggle" href="#" role="button" data-toggle="dropdown"> Dropdown </a>
          <div class="dropdown-menu">
            <a class="dropdown-item" href="#"> 1 </a>
            <a class="dropdown-item" href="#"> 2 </a>
            <a class="dropdown-item" href="#"> 3 </a>
            <a class="dropdown-item" href="#"> 4 </a>
          </div>
        </li>
      </ul>
    </div>
  </nav>


  <!-- second navbar with top offset -->
  <nav class="navbar bg-primary fixed-top navbar-expand-sm">
    <p>hello world</p>
  </nav>

</body>

</html>

Answer 2

添加了两个类.front和.back，并更新了z-index值。

更新了JSFiddle

CSS：

.front{
 z-index: 2000 !important;
}
.back{
 z-index: -1 !important; 
}

HTML：

<!-- first navbar with dropdown-menu -->
<nav class="navbar bg-dark fixed-top navbar-expand-sm front">
  <div class="collapse navbar-collapse">
    <ul class="navbar-nav">
      <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="#" role="button" data-toggle="dropdown"> Dropdown </a>
        <div class="dropdown-menu">
          <a class="dropdown-item" href="#"> 1 </a>
              <a class="dropdown-item" href="#"> 2 </a>
          <a class="dropdown-item" href="#"> 3 </a>
          <a class="dropdown-item" href="#"> 4 </a>
        </div>
      </li>
    </ul>
  </div>
</nav>


<!-- second navbar with top offset -->
<nav class="navbar bg-primary fixed-top navbar-expand-sm back" style="top:56px!important;">
<p>hello world</p>
</nav>

对z-index-https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Positioning/Understanding_z_index/Adding_z-index的引用

第二个引导导航栏与第一个导航栏的下拉菜单重叠？

2 个答案: